783 research outputs found
Performance of Electrical Spectroscopy using a Resper Probe to Measure the Salinity and Water Content of Concrete or Terrestrial Soil
This paper discusses the performance of electrical spectroscopy using a
RESPER probe to measure the salinity s and volumetric content {\theta}W of the
water in concrete or terrestrial soil. The RESPER probe is an induction device
for spectroscopy which performs simultaneous and non invasive measurements of
the electrical RESistivity 1/{\sigma} and relative dielectric PERmittivity
{\epsilon}r of a subjacent medium. Numerical simulations establish that the
RESPER can measure {\sigma} and {\epsilon} with inaccuracies below a predefined
limit (10%) up to the high frequency band (HF). Conductivity is related to
salinity and dielectric permittivity to volumetric water content using suitably
refined theoretical models which are consistent with the predictions of
Archie's and Topp's empirical laws. The better the agreement, the lower the
hygroscopic water content and the higher s; so closer agreement is found with
concrete containing almost no bonded water molecules provided these are
characterized by a high {\sigma}. A novelty of the present paper is the
application of a mathematical- physical model to the propagation of errors in
the measurements, based on a sensitivity functions tool. The inaccuracy of
salinity (water content) is the ratio (product) between the conductivity
(permittivity) inaccuracy, specified by the probe, and the sensitivity function
of salinity (water content) relative to conductivity (permittivity), derived
from the constitutive equations of the medium. The main result is the model's
prediction that the lower the inaccuracy for the measurements of s and
{\theta}W (decreasing by as much as an order of magnitude from 10% to 1%), the
higher {\sigma}; so the inaccuracy for soil is lower.Comment: 45 pages, 5 figures, 1 tabl
Response robustness and safety against jump to contact in AFMs controlled via different techniques
The role of a global dynamics analysis to assess a system robustness and actual safety in operating conditions is investigated by studying the effect of different local and global control techniques on the nonlinear behavior of a noncontact AFM via dynamical integrity concepts and tools
Nonlinear dynamics and control in macro/micro-mechanics: some computational issues
Computational issues in the global dynamics of two systems in micro- and macro-mechanics, with different dimensionality, are addressed. Attention is focused on calculation of integrity measures, determination of saddle manifolds undergoing global bifurcations, implementation of a control procedure for delaying basins erosion, selection of 2D cross-sections of multidimensional basins of attraction for understanding the role of transient dynamics in the global scenario of coupled steady responses
Nonlinear vibrations of symmetric cross-ply laminates via thermomechanically coupled reduced order models
Thermomechanically coupled, geometrically nonlinear, laminated plates are addressed through a unified 2D formulation, by considering classical and third-order shear-deformable von Karman models, along with correspondingly consistent linear and cubic variations of the temperature along the thickness. Minimal dimension reduction of the mechanical problem is accomplished for symmetric cross-ply laminates, ending up for both models to a coupled three-mode reduced model with terms and coefficients of variable nature depending on the variety of mechanical and/or thermal excitations. Nonlinear vibrations of the classical model are investigated in conditions of thermal dynamics either passively entrained by the harmonically varying transverse load via the existing coupling terms, or also playing some active role owed to a temperature difference with respect to the surrounding medium
Coherent Control of Stimulated Emission Inside one Dimensional Photonic Crystals — Strong Coupling Regime
The present book chapter discusses the stimulated emission, in strong coupling regime, of an atom embedded inside a one dimensional (1D) Photonic Band Gap (PBG) cavity which is pumped by two counter-propagating laser beams. Quantum electrodynamics is applied to model the atom-field interaction, by considering the atom as a two level system, the e.m. field as a superposition of normal modes, the
coupling in dipole approximation, and the equations of motion in Wigner-Weisskopf and rotating wave approximations. In addition, the Quasi Normal Mode (QNM) approach for an open cavity is adopted, interpreting the local density of states (LDOS) as the local density of probability to excite one QNM of the cavity; and therefore rendering this LDOS dependent on the phase difference of the two laser beams. In this book chapter we demonstrate that the strong coupling regime occurs at high values of the LDOS. In accordance with the results of the literature, the emission probability of the atom decays with an oscillatory behaviour,
so that the atomic emission spectrum exhibits two peaks (Rabi splitting). The novelty of this book chapter is that
the phase difference of the two laser beams can produce a coherent control of both the oscillations for the atomic emission probability and, as a consequence, of the Rabi splitting in the emission spectrum. Possible criteria to design active delay lines are finally discussed
Bifurcation scenarios, dynamical integrity and control of noncontact atomic force microscopes
The research focuses on the description of the global dynamical behavior of a reduced-order model of noncontact Atomic Force Microscope. Different numerical analyses and continuation techniques are carried out to investigate the evolution of the main system periodic solutions and relevant basins of attraction under variations of the most significant system parameters. Local bifurcations, stability boundaries and basin erosion processes around primary and subharmonic resonance regions are studied in presence of both the parametrical horizontal excitation and the external one, and the obtained behavior charts are used not only to compare the results with the literature ones, but also as practical instruments to characterize the operation ranges in terms of the selected parameters. With the same perspective, dynamical integrity concepts, such as detection of basins of attraction, and quantification of their erosion process via integrity measures, are applied to determine acceptable frequency-dependent thresholds associated with a priori safe design targets.
Furthermore, an external feedback control is introduced with the aim to take the system response to a selected reference one, thus providing a simple and efficient method to avoid possible unstable motions. Upon checking the effectiveness of the procedure in the weakly nonlinear regime via a perturbation approach, several numerical analyses in the strongly nonlinear regime are accomplished to achieve a description of its dynamical behavior as a function of the newly inserted parameters, and to critically evaluate the effectiveness of the control actuation on the system dynamics, with also a view to the overall response scenario
Design Of An Induction Probe For Simultaneous Measurements Of Permittivity And Resistivity
In this paper, we propose a discussion of the theoretical design and move
towards the development and engineering of an induction probe for electrical
spectroscopy which performs simultaneous and non invasive measurements on the
electrical RESistivity \rho and dielectric PERmittivity \epsilon r of
non-saturated terrestrial ground and concretes (RESPER probe). In order to
design a RESPER which measures \rho and \epsilon r with inaccuracies below a
prefixed limit (10%) in a band of low frequencies (LF) (B=100kHz), the probe
should be connected to an appropriate analogical digital converter (ADC), which
samples in uniform or in phase and quadrature (IQ) mode, otherwise to a lock-in
amplifier. The paper develops only a suitable number of numerical simulations,
using Mathcad, which provide the working frequencies, the electrode-electrode
distance and the optimization of the height above ground minimizing the
inaccuracies of the RESPER, in galvanic or capacitive contact with terrestrial
soils or concretes, of low or high resistivity. As findings of simulations, we
underline that the performances of a lock-in amplifier are preferable even when
compared to an IQ sampling ADC with high resolution, under the same operating
conditions. As consequences in the practical applications: if the probe is
connected to a data acquisition system (DAS) as an uniform or an IQ sampler,
then it could be commercialized for companies of building and road paving,
being employable for analyzing "in situ" only concretes; otherwise, if the DAS
is a lock-in amplifier, the marketing would be for companies of geophysical
prospecting, involved to analyze "in situ" even terrestrial soils.Comment: 37 pages, 7 figures, 3 table
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